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Solar activated, time delayed, chicken door release. 24VDC is supplied by a 1.5W solar cell trickle charger which charges the main 12VDC battery, as well as causing a comparator to hold a monostable 555 trigger to ground via NMOS, illuminating an amber LED indicator and keeping the 555 output high. That high output charges the solenoid pulse length capacitor while holding its discharge PMOS closed. When the solar cell falls below 12VDC (darkness) the comparator closes the trigger NMOS, triggering the 555 timer. When the 555 timer capacitor discharges (set short for the simulation) the 555 output switches to low, opening a PMOS and discharging the capacitor into an NMOS, energizing the solenoid for 1 second and releasing the latch holding up the chicken coup gate door, (represented here by an LED) and illuminating the ‘triggered’ LED indicator. The next day when the solar cell voltage rises above 12VDC, the system resets and begins to recharge the battery. When I feed the chickens in the AM, I manually raise and latch the gate.
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